Chill cast iron alloy



Patented Jan. 22, 1935 UNITED STATES PATENT OFFICE emu. cas'r IRON ALLOYporation of Delaware No Drawing. Original application October 21,

1926, Sfl'lal No. 143,293. Divided and one application June 6, 1934,Serial No. 129,290

Claims.

This invention relates to alloys and more especially to chill castnickel bearing iron alloys.

The invention relates particularly to castings formed.- by castingnickel bearing iron compositions against chills to form castings havingextreme hardness in the chilled portion and improved toughness andstrength in. the chilled portion and in the gray iron adjacent thechilled portion. This material is well adapted for chilled iron wearingparts which require strength and toughness, for example, hot or coldrolls for glass and metal working, cams, gears,. dies, stamps and likeparts subjected to impact or heavy pressure. Our improved composition ischaracterized by its strength, hardness and toughnessqualities desirablein wearing parts.

We have obtained good results in practice with compositions within thefollowing general ranges:

Percent Carbon 2-4 Silicon .25-2 'Manganesen, .25 -2 Nickel 2 -10Chrommium Up to4 Phosphorous and sulphur may be present within theranges usually found in cast iron, as for instance, phosphorus .03 to1.15% and sulphur .03 to 25%. See any edition of Kents handbook, 1900and later; Moldenke, Principles of Iron Founding, edition of 1917, page198; Hatfield, Cast Iron in the Light of Recent Research; and others. Inrespect to the ranges of phosphorus and sulphur in chilled, white andgray iron castings such as for rolls, cams, brake shoes, gears, plowpoints, etc., phosphorus ranges from, under .10 to 1.0% and sulphur .04to 25%. See particularly pages 196, 182, 183, 199 and 198 in their orderof Moldenkes Principles of Iron Founding, 1917, where both thephosphorus and sulphur for chilled rolls must be, under .3 and 08%respectively, and for chilled castings in general. As indicated on page183, the phosphorus and sulphur shall be, below .20 and .06%respectively. On page 199, it is shown Again, the sulphur and phosphoruspercentages givenexcept where wanted high, can be anything below thefigures. In addition, page 198, there is a statement as to thepercentages in the tables on the pages noted that The tables of analysesgiven in the above classification of castings must, as was said at theoutset, be considered only as typical. Again, in Kents MechanicalEngineers Handbook, edition printed in 1923, attention is called to page434, wherein sulphur is recited from .05 to .20% and it states in thelower part of that page and in respect to the above sulphur content-Inthis composition phosphorus is supposed to be well below .10%. It isalso to be noted that the ranges of analyses of American, as well asforeign, pig irons, are good indications of castings produced from pigirons as very often a definite and consistent type of pig iron must beused. Such ranges are to be found in Appendix II of Hatflelds Cast Ironin the Light of Recent Research, second edition 1918 and third edition1928.

- The composition may be varied somewhat, if desired, by the addition ofother alloying materials, such as molybdenum, tungsten, titanium,copper, etc. The carbon content is within the general range usual forcast iron, from either air furnace orcupola.

Casting compositions l ing within those ranges are particularlydesirable in that good adjustment of nickel, chromium, silicon andcarbon contents is secured to nicely regulate the depth of chill.

We find that the amount of chill in the chill cast iron may bemaintained sensibly constant if nickel and chromium are added asalloying materials in about the ratio of 2 or 3 to 1, say about 2 to 1.We also find thatthe amount of chill may be nicely controlled bysuitably adjusting the various elements according to the rough rule that1 part carbon equals 3 parts silicon, 1 part silicon equals 2 partsnickel, 1 part chromium equals 2 parts nickel, and 1 part sulphur equals10 parts silicon; increasing the silicon, carbon and nickel acts todecrease the chill, whereas, increasing the chromium and sulphur acts toincrease the chill. The silicon and carbon contents may be lowered, ifdesired, by using a higher ratio of nickel to chromium than thatmentioned above, the increased chilling tendency accompanying thelowered' silicon and carbon contents being counteracted by the highernickel content. It is to be noted that the foregoing is to be taken intoconsideration in connection with the statement and expression usedherein that the nickel is present in the proportion of 2 or 3 to 1 ofchromium.

For ordinary work, however, we have obtained good results with acomposition containing about the following percentages:

Phosphorus and sulphur may be present within the ranges usually found incast iron, as indicated above.

Such a composition, ii chill cast, will give a white iron having'aBrinell hardness of 550, as compared with the 400-500 of ordinarychilled iron. The chilled metal under tension has a transverse strengthoi 8000 pounds for 1 inch square bars tested on 12 inch centers incomparison with about 6000 pounds for ordinary high carbon chilled iron.Gray iron having ,this composition. has a tensile strength of about35,000 pounds per' dition. These characteristics render the compositiondesirable for chilled castings to be subjected to heavy pressure orimpact, since such castings are less liable to breakage than ordinarychilled iron castings.

We are aware that nickel has been proposed as an addition material toreduce the chilling effect in iron alloys, and that chromium has beenproposed as a hardener. We have found, however, that a proper proportionshould be maintained between the nickel and chromium with respect to thesilicon and carbon if the composition is to be rendered hard, and yettough and v strong. By properly proportioning the alloying elements, wehave produced and improved iron alloy adapted to be chill cast to forman exceedingly hard and tough white iron with a strong, tough gray ironadjacent thereto.

We have found that the hardness of chilled cast iron castings made underour invention is due to the fact that the matrix portion of the iron ischanged from the softer pearlite of ordinary chilled iron castings intothe harder martensite or troostite. Martensite is often associated withaustenite and hence by martensite, we mean martensite or austenite orboth in association. Hence the resulting hardness is between that of thevery hard iron carbide grains and the martensite having a Brinellhardness of from 550 up to about 750 where the carbon is about 3.50%.This hardness may be regulated somewhat by proportions of the alloy orthe use of equivalents.

A further important advantage of our invention resides in the provisionof an improved chill casting alloy wherein the depth of chill may benicely controlled by suitable adjustment of the.

addition elements. Cast iron 01 our composition may be made either inthe air furnace or cupola, and we intend to cover such composition of;cast iron made in either type of furnace.

The present application is a divisional case of.

our co-pending application,'Serial No. 143,293, filed October 21, 1926.We claim:

1. A cast iron alloy containingirom about 2 to about 2.5% carbon, about2% nickel, from about .25 to about 2% chromium and wherein the nickelcontent bears a relation of approximately three to one of the chromiumcontent.

2. A chilled iron casting containing from about 2 to about 2.5% carbon,about 2% nickel, from about;. 25 to about 2% chromium and wherein thenickel content bears a relation 01 approximately three to one of thechromium content.

.3. An iron roll containing from about 2 to about 25% carbon, about 2%nickel, from about .25 to about 2% chromium and wherein the nickelcontent bears a-- relation of approximately three to one of the chromiumcontent.

4. A'cast iron alloy containing from about 2 to about 2.5% carbon, about2% nickel, from about .25 to about 2% chromium, and a small buteffective amount of molybdenum, and wherein the nickel content bearsarelation of approximately three to one of the chromium content.

5. A chilled iron casting containing from about 2 to about 2.5% carbon,about 2% nickel, from about .25 to about 2% chromium, and a small buteffective amount of molybdenum, and wherein thenickelcontent bears arelation of approximately three to one of the chromium content 6. Aniron roll containing from about 2 to about 2.5% carbon, about 2% nickel,from about .25 to about 2% chromium, and a small but eilective amount ofmolybdenum, and wherein the nickel icontent bears a relation ofapproximately three ,to one of the chromium content.

7. A cast iron alloy containing from about 2 to about 2.5% carbon, about2% nickel, from about .25 to about 2% chromium and a small but eifectiveamount up to about 2% of silicon and a small but eifective amount up toabout 2% of manganese, and wherein the nickel content bears a relationof approximately three to one of the chromium content.

8. 'Acast iron. alloy containing from about 2 to about 2.5% carbon,about 2%.nickel, from about .25 to about 2% chromium, about 0.25% toabout 2% of silicon, about 0.25% to about 2% of manganese, and a smallbut effective amount of molybdenum, and wherein the nickel content bearsa relation of approximately 3 to 1 of the the nickel content bears arelation of approxi-' mately 3 to 1 of the chromium content.

PAULD. MERICA.

JAMES S. VANICK.

THOMAS H. WICKENDEN.

